import java.util.Scanner;

public class Draw {
    public static void main(String[] args) {
        long[] dp = new long[21];
        dp[0] = dp[1] = 0;
        dp[2] = 1;
        long[] f = new long[21];
        f[0] = f[1] = 1;
        f[2] = 2;
        for(int i = 3; i <= 20; i++) {
            dp[i] = (i - 1) * (dp[i - 1] + dp[i - 2]);
            f[i] = i * f[i - 1];
        }
        Scanner s = new Scanner(System.in);
        while(s.hasNextInt()) {
            int n = s.nextInt();
            System.out.printf("%.2f%%\n",100.0 * dp[n]/f[n]);
        }
    }
}
